Continuing advances are being made in the field of computers and related peripheral equipment. These advances often include an increased speed of operation and/or an increase in the rate at which data can be exchanged between connected devices. Users do not immediately discard their existing equipment when improved equipment becomes available. Instead, they often prefer to recoup their investment and use their existing equipment for the duration of its useful life. As a result, a system is often upgraded and replaced piece-by-piece as each item nears the end of its useful life.
Generally, newer equipment can operate at a higher speed or data rate than can older equipment. When a data processing system user updates his system, it is important that the higher data rates of the newly acquired equipment be utilized where possible. It is also desirable that the data rate of the new equipment be controllable to provide backward compatibility with older system elements that have lower data rates.
The above compatibility requirements are particularly desirable with respect to a computer and its peripherals such as disk drives and tape drives. A computer is typically equipped with a control board, termed a floppy controller, which permits the computer to communicate with the disk or tape drive (hereinafter drive). A system user may replace a controller or an existing low speed drive with a newer drive capable of operating at a plurality of speeds including speeds that are higher than that of the drive being replaced. It is necessary when such a replacement is made that the new controller or drive be advised as to the speed at which it should operate so that both the drive and the controller operate at the maximum possible data rate common to both devices. Speed compatibility is desirable so that a drive can record data at different rates and so that a tape written at a high data rate by one drive can be read by another drive operating at a lower data rate.
It is heretofore been difficult to achieve this maximum common data rate since it required the computer user to perform manual operations as well as to have knowledge of the capabilities of both the floppy controller and the new disk drive. The manual operations were required so that appropriate control signals could be transmitted under user control to the drive instructing it to operate at the highest data rate common to both the floppy controller and the drive. Also, knowledge of the data rate capabilities of these devices is often not readily available. Even if available, it can often only be obtained by pursuing the operational manuals for the connected devices. It may therefore be seen that it is a problem in data processing systems to cause a new newly installed drive to operate with its connected floppy interface at the highest data rate common to both devices.